(a) Technical Field
The present invention relates to a molding apparatus and method for fixing permanent magnets of a rotor. More particularly, the present invention relates to an apparatus and method for fixing permanent magnets in a rotor core during production of drive motors for environmental vehicles.
(b) Background Art
Drive motors are used as a power source in environmental vehicles such as hybrid vehicles and electric vehicles. Like typical motors, the key components of the drive motor include a stator, in which a coil is wound on a stator core, and a rotor disposed inside the stator. A rotor can best be defined as a structure in which permanent magnets are inserted into a rotor core.
More specifically, an Nd—Fe permanent magnet synchronous motor is mainly used as the drive motor to allow the drive motor to be mounted in a limited amount of space within an engine room of a vehicle, and the permanent magnets are fixed in a rotor core made of a non-oriented electrical steel sheet.
Conventionally, in order to fix the permanent magnets in the rotor core for the drive motor, a method of applying an adhesive to the permanent magnets or to magnet insertion apertures (into which the permanent magnets are to be inserted) of the rotor core, inserting the permanent magnets into the magnet insertion apertures, and then curing the adhesive or a method of injecting a resin into the magnet insertion apertures of the rotor core, into which the permanent magnets are inserted, and then curing the resin is generally used.
FIG. 1A shows a schematic diagram illustrating a process of disposing a rotor core, into which permanent magnets are inserted, between an upper mold and a lower mold and injecting a resin into a space between the rotor core and the permanent magnets and FIG. 1B is a perspective view illustrating the problems associated with the rotor core in which the permanent magnets are embedded by the related art method.
As shown in FIGS. 1A-B, when a rotor core 15 into which permanent magnets are inserted is disposed into an upper mold 11 and a lower mold 12 and a resin is injected into a space between the rotor core 15 and the permanent magnets 17 through the lower mold 12 (or upper mold) so that the permanent magnets 17 are fixed in the rotor core 15 according to the related art, the positions of the permanent magnets 17 arranged in the circumferential direction of the rotor core 15 do not coincide with each other in the axial direction of the rotor core.
Typically, the permanent magnets to be inserted into the rotor core are smaller than the magnet insertion apertures of the core. The reason for this is to facilitate the insertion of the permanent magnets, to prevent the surface coating, which his applied to increase the corrosion resistance, of the permanent magnet from being damaged by fire, and in particular to form a gap between the permanent magnets and the rotor core, thus providing an area for the injection of adhesive or resin. Moreover, the reason that the size of the permanent magnet is smaller than that of the magnet insertion aperture with respect to the axial direction of the rotor core is to prevent the permanent magnets from being broken by components to be connected to both sides of the core subsequently.
Accordingly, when the permanent magnets 17 are fixed in the magnet insertion apertures 16 of the rotor core 15 using resin according to the related art, as shown in FIG. 1, the positions of the permanent magnets 17 inserted into the magnet insertion apertures 16 may not always be the same, and it is difficult to control the flow of the resin injected into the magnet insertion apertures 16 in an orderly manner. Thus, the positions of the permanent magnets 17 inserted into the magnet insertion apertures 16 of the rotor core 15 may not coincide with each other.
As such, when the positions of the permanent magnets fixed in the rotor core do not coincide with each other in the axial direction, the motor control performance is deteriorated due to imbalance of a rotor assembly, and electromagnetic noise increases as a result. Moreover, it is necessary to add a process for reducing the unbalance of the rotor assembly to rectify the above-described problems, which results in an increase in costs associated with manufacturing a motor.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.